Precision localization of single atom via phase-dependent quantum coherence in three dimensions

We present a new scheme for high-efficiency three-dimensional (3D) atom localization in a four-level atomic system via measuring the populations in two excited states. Owing to the space-dependent atom–field interaction, the position probability distribution of the atom passing through the standing waves can be directly determined by measuring the populations in two excited states. It is found that the phase-sensitive property of the atomic system reduces the uncertainty in the position measurement of the atom. In particular, the probability of finding the atom in 3D space can be almost 100% via properly varying the parameters of the system. Our scheme opens a promising way to achieve high-precision and high-efficiency 3D atom localization, which provides some potential applications in the atom nanolithography via 3D atom localization. (letter)